// ASM: a very small and fast Java bytecode manipulation framework
// Copyright (c) 2000-2011 INRIA, France Telecom
// All rights reserved.
//
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// modification, are permitted provided that the following conditions
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//    notice, this list of conditions and the following disclaimer in the
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package org.springframework.asm;

/**
 * A non standard class, field, method or Code attribute, as defined in the Java Virtual Machine
 * Specification (JVMS).
 *
 * @author Eric Bruneton
 * @author Eugene Kuleshov
 * @see <a href= "https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7">JVMS
 * 4.7</a>
 * @see <a href= "https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7.3">JVMS
 * 4.7.3</a>
 */
public class Attribute {

	/**
	 * The type of this attribute, also called its name in the JVMS.
	 */
	public final String type;

	/**
	 * The raw content of this attribute, only used for unknown attributes (see {@link #isUnknown()}).
	 * The 6 header bytes of the attribute (attribute_name_index and attribute_length) are <i>not</i>
	 * included.
	 */
	private byte[] content;

	/**
	 * The next attribute in this attribute list (Attribute instances can be linked via this field to
	 * store a list of class, field, method or Code attributes). May be {@literal null}.
	 */
	Attribute nextAttribute;

	/**
	 * Constructs a new empty attribute.
	 *
	 * @param type the type of the attribute.
	 */
	protected Attribute(final String type) {
		this.type = type;
	}

	/**
	 * Returns {@literal true} if this type of attribute is unknown. This means that the attribute
	 * content can't be parsed to extract constant pool references, labels, etc. Instead, the
	 * attribute content is read as an opaque byte array, and written back as is. This can lead to
	 * invalid attributes, if the content actually contains constant pool references, labels, or other
	 * symbolic references that need to be updated when there are changes to the constant pool, the
	 * method bytecode, etc. The default implementation of this method always returns {@literal true}.
	 *
	 * @return {@literal true} if this type of attribute is unknown.
	 */
	public boolean isUnknown() {
		return true;
	}

	/**
	 * Returns {@literal true} if this type of attribute is a Code attribute.
	 *
	 * @return {@literal true} if this type of attribute is a Code attribute.
	 */
	public boolean isCodeAttribute() {
		return false;
	}

	/**
	 * Returns the labels corresponding to this attribute.
	 *
	 * @return the labels corresponding to this attribute, or {@literal null} if this attribute is not
	 * a Code attribute that contains labels.
	 */
	protected Label[] getLabels() {
		return new Label[0];
	}

	/**
	 * Reads a {@link #type} attribute. This method must return a <i>new</i> {@link Attribute} object,
	 * of type {@link #type}, corresponding to the 'length' bytes starting at 'offset', in the given
	 * ClassReader.
	 *
	 * @param classReader         the class that contains the attribute to be read.
	 * @param offset              index of the first byte of the attribute's content in {@link ClassReader}. The 6
	 *                            attribute header bytes (attribute_name_index and attribute_length) are not taken into
	 *                            account here.
	 * @param length              the length of the attribute's content (excluding the 6 attribute header bytes).
	 * @param charBuffer          the buffer to be used to call the ClassReader methods requiring a
	 *                            'charBuffer' parameter.
	 * @param codeAttributeOffset index of the first byte of content of the enclosing Code attribute
	 *                            in {@link ClassReader}, or -1 if the attribute to be read is not a Code attribute. The 6
	 *                            attribute header bytes (attribute_name_index and attribute_length) are not taken into
	 *                            account here.
	 * @param labels              the labels of the method's code, or {@literal null} if the attribute to be read
	 *                            is not a Code attribute.
	 * @return a <i>new</i> {@link Attribute} object corresponding to the specified bytes.
	 */
	protected Attribute read(
			final ClassReader classReader,
			final int offset,
			final int length,
			final char[] charBuffer,
			final int codeAttributeOffset,
			final Label[] labels) {
		Attribute attribute = new Attribute(type);
		attribute.content = new byte[length];
		System.arraycopy(classReader.classFileBuffer, offset, attribute.content, 0, length);
		return attribute;
	}

	/**
	 * Returns the byte array form of the content of this attribute. The 6 header bytes
	 * (attribute_name_index and attribute_length) must <i>not</i> be added in the returned
	 * ByteVector.
	 *
	 * @param classWriter the class to which this attribute must be added. This parameter can be used
	 *                    to add the items that corresponds to this attribute to the constant pool of this class.
	 * @param code        the bytecode of the method corresponding to this Code attribute, or {@literal null}
	 *                    if this attribute is not a Code attribute. Corresponds to the 'code' field of the Code
	 *                    attribute.
	 * @param codeLength  the length of the bytecode of the method corresponding to this code
	 *                    attribute, or 0 if this attribute is not a Code attribute. Corresponds to the 'code_length'
	 *                    field of the Code attribute.
	 * @param maxStack    the maximum stack size of the method corresponding to this Code attribute, or
	 *                    -1 if this attribute is not a Code attribute.
	 * @param maxLocals   the maximum number of local variables of the method corresponding to this code
	 *                    attribute, or -1 if this attribute is not a Code attribute.
	 * @return the byte array form of this attribute.
	 */
	protected ByteVector write(
			final ClassWriter classWriter,
			final byte[] code,
			final int codeLength,
			final int maxStack,
			final int maxLocals) {
		return new ByteVector(content);
	}

	/**
	 * Returns the number of attributes of the attribute list that begins with this attribute.
	 *
	 * @return the number of attributes of the attribute list that begins with this attribute.
	 */
	final int getAttributeCount() {
		int count = 0;
		Attribute attribute = this;
		while (attribute != null) {
			count += 1;
			attribute = attribute.nextAttribute;
		}
		return count;
	}

	/**
	 * Returns the total size in bytes of all the attributes in the attribute list that begins with
	 * this attribute. This size includes the 6 header bytes (attribute_name_index and
	 * attribute_length) per attribute. Also adds the attribute type names to the constant pool.
	 *
	 * @param symbolTable where the constants used in the attributes must be stored.
	 * @return the size of all the attributes in this attribute list. This size includes the size of
	 * the attribute headers.
	 */
	final int computeAttributesSize(final SymbolTable symbolTable) {
		final byte[] code = null;
		final int codeLength = 0;
		final int maxStack = -1;
		final int maxLocals = -1;
		return computeAttributesSize(symbolTable, code, codeLength, maxStack, maxLocals);
	}

	/**
	 * Returns the total size in bytes of all the attributes in the attribute list that begins with
	 * this attribute. This size includes the 6 header bytes (attribute_name_index and
	 * attribute_length) per attribute. Also adds the attribute type names to the constant pool.
	 *
	 * @param symbolTable where the constants used in the attributes must be stored.
	 * @param code        the bytecode of the method corresponding to these Code attributes, or {@literal
	 *                    null} if they are not Code attributes. Corresponds to the 'code' field of the Code
	 *                    attribute.
	 * @param codeLength  the length of the bytecode of the method corresponding to these code
	 *                    attributes, or 0 if they are not Code attributes. Corresponds to the 'code_length' field of
	 *                    the Code attribute.
	 * @param maxStack    the maximum stack size of the method corresponding to these Code attributes, or
	 *                    -1 if they are not Code attributes.
	 * @param maxLocals   the maximum number of local variables of the method corresponding to these
	 *                    Code attributes, or -1 if they are not Code attribute.
	 * @return the size of all the attributes in this attribute list. This size includes the size of
	 * the attribute headers.
	 */
	final int computeAttributesSize(
			final SymbolTable symbolTable,
			final byte[] code,
			final int codeLength,
			final int maxStack,
			final int maxLocals) {
		final ClassWriter classWriter = symbolTable.classWriter;
		int size = 0;
		Attribute attribute = this;
		while (attribute != null) {
			symbolTable.addConstantUtf8(attribute.type);
			size += 6 + attribute.write(classWriter, code, codeLength, maxStack, maxLocals).length;
			attribute = attribute.nextAttribute;
		}
		return size;
	}

	/**
	 * Returns the total size in bytes of all the attributes that correspond to the given field,
	 * method or class access flags and signature. This size includes the 6 header bytes
	 * (attribute_name_index and attribute_length) per attribute. Also adds the attribute type names
	 * to the constant pool.
	 *
	 * @param symbolTable    where the constants used in the attributes must be stored.
	 * @param accessFlags    some field, method or class access flags.
	 * @param signatureIndex the constant pool index of a field, method of class signature.
	 * @return the size of all the attributes in bytes. This size includes the size of the attribute
	 * headers.
	 */
	static int computeAttributesSize(
			final SymbolTable symbolTable, final int accessFlags, final int signatureIndex) {
		int size = 0;
		// Before Java 1.5, synthetic fields are represented with a Synthetic attribute.
		if ((accessFlags & Opcodes.ACC_SYNTHETIC) != 0
				&& symbolTable.getMajorVersion() < Opcodes.V1_5) {
			// Synthetic attributes always use 6 bytes.
			symbolTable.addConstantUtf8(Constants.SYNTHETIC);
			size += 6;
		}
		if (signatureIndex != 0) {
			// Signature attributes always use 8 bytes.
			symbolTable.addConstantUtf8(Constants.SIGNATURE);
			size += 8;
		}
		// ACC_DEPRECATED is ASM specific, the ClassFile format uses a Deprecated attribute instead.
		if ((accessFlags & Opcodes.ACC_DEPRECATED) != 0) {
			// Deprecated attributes always use 6 bytes.
			symbolTable.addConstantUtf8(Constants.DEPRECATED);
			size += 6;
		}
		return size;
	}

	/**
	 * Puts all the attributes of the attribute list that begins with this attribute, in the given
	 * byte vector. This includes the 6 header bytes (attribute_name_index and attribute_length) per
	 * attribute.
	 *
	 * @param symbolTable where the constants used in the attributes must be stored.
	 * @param output      where the attributes must be written.
	 */
	final void putAttributes(final SymbolTable symbolTable, final ByteVector output) {
		final byte[] code = null;
		final int codeLength = 0;
		final int maxStack = -1;
		final int maxLocals = -1;
		putAttributes(symbolTable, code, codeLength, maxStack, maxLocals, output);
	}

	/**
	 * Puts all the attributes of the attribute list that begins with this attribute, in the given
	 * byte vector. This includes the 6 header bytes (attribute_name_index and attribute_length) per
	 * attribute.
	 *
	 * @param symbolTable where the constants used in the attributes must be stored.
	 * @param code        the bytecode of the method corresponding to these Code attributes, or {@literal
	 *                    null} if they are not Code attributes. Corresponds to the 'code' field of the Code
	 *                    attribute.
	 * @param codeLength  the length of the bytecode of the method corresponding to these code
	 *                    attributes, or 0 if they are not Code attributes. Corresponds to the 'code_length' field of
	 *                    the Code attribute.
	 * @param maxStack    the maximum stack size of the method corresponding to these Code attributes, or
	 *                    -1 if they are not Code attributes.
	 * @param maxLocals   the maximum number of local variables of the method corresponding to these
	 *                    Code attributes, or -1 if they are not Code attribute.
	 * @param output      where the attributes must be written.
	 */
	final void putAttributes(
			final SymbolTable symbolTable,
			final byte[] code,
			final int codeLength,
			final int maxStack,
			final int maxLocals,
			final ByteVector output) {
		final ClassWriter classWriter = symbolTable.classWriter;
		Attribute attribute = this;
		while (attribute != null) {
			ByteVector attributeContent =
					attribute.write(classWriter, code, codeLength, maxStack, maxLocals);
			// Put attribute_name_index and attribute_length.
			output.putShort(symbolTable.addConstantUtf8(attribute.type)).putInt(attributeContent.length);
			output.putByteArray(attributeContent.data, 0, attributeContent.length);
			attribute = attribute.nextAttribute;
		}
	}

	/**
	 * Puts all the attributes that correspond to the given field, method or class access flags and
	 * signature, in the given byte vector. This includes the 6 header bytes (attribute_name_index and
	 * attribute_length) per attribute.
	 *
	 * @param symbolTable    where the constants used in the attributes must be stored.
	 * @param accessFlags    some field, method or class access flags.
	 * @param signatureIndex the constant pool index of a field, method of class signature.
	 * @param output         where the attributes must be written.
	 */
	static void putAttributes(
			final SymbolTable symbolTable,
			final int accessFlags,
			final int signatureIndex,
			final ByteVector output) {
		// Before Java 1.5, synthetic fields are represented with a Synthetic attribute.
		if ((accessFlags & Opcodes.ACC_SYNTHETIC) != 0
				&& symbolTable.getMajorVersion() < Opcodes.V1_5) {
			output.putShort(symbolTable.addConstantUtf8(Constants.SYNTHETIC)).putInt(0);
		}
		if (signatureIndex != 0) {
			output
					.putShort(symbolTable.addConstantUtf8(Constants.SIGNATURE))
					.putInt(2)
					.putShort(signatureIndex);
		}
		if ((accessFlags & Opcodes.ACC_DEPRECATED) != 0) {
			output.putShort(symbolTable.addConstantUtf8(Constants.DEPRECATED)).putInt(0);
		}
	}

	/**
	 * A set of attribute prototypes (attributes with the same type are considered equal).
	 */
	static final class Set {

		private static final int SIZE_INCREMENT = 6;

		private int size;
		private Attribute[] data = new Attribute[SIZE_INCREMENT];

		void addAttributes(final Attribute attributeList) {
			Attribute attribute = attributeList;
			while (attribute != null) {
				if (!contains(attribute)) {
					add(attribute);
				}
				attribute = attribute.nextAttribute;
			}
		}

		Attribute[] toArray() {
			Attribute[] result = new Attribute[size];
			System.arraycopy(data, 0, result, 0, size);
			return result;
		}

		private boolean contains(final Attribute attribute) {
			for (int i = 0; i < size; ++i) {
				if (data[i].type.equals(attribute.type)) {
					return true;
				}
			}
			return false;
		}

		private void add(final Attribute attribute) {
			if (size >= data.length) {
				Attribute[] newData = new Attribute[data.length + SIZE_INCREMENT];
				System.arraycopy(data, 0, newData, 0, size);
				data = newData;
			}
			data[size++] = attribute;
		}
	}
}
